The present invention relates to an industrial robot in which a power source for sensors is incorporated.
In recent industrial robots, a controller and a manipulator are provided separately from each other in most cases. Meanwhile, the controller is provided with sensors for feeding back to the controller signals on position and angle or velocity of the manipulator.
Generally, a conventional industrial robot of this kind has such an arrangement as shown in FIGS. 4 and 5. The known industrial robot includes a controller 1, a manipulator 2, sensors 4 mounted on motors 3 of the manipulators 2, respectively and a cable 5 for transmitting feedback signals of the sensors 4 to the controller 1.
In the known industrial robot of the above described arrangement, a power source 6 for supplying electric power to the sensors 4 is incorporated in the controller 1.
Meanwhile, after the power source 6 has been turned off, a battery for effecting backup of current position of the manipulator 2 is required to be connected to the sensors 4. Furthermore, a function of resetting backup values of the manipulator 2 may be furnished for maintenance purposes. When the backup values of the manipulator 2 are reset, resetting cables of the sensors 4 are usually short-circuited to a power cable.
In this prior art industrial robot in which the power source 6 for the sensors 4 is incorporated in the controller 1, length of the cable 5 for connecting the controller 1 and the manipulator 2 is limited. Namely, potential difference is produced between the power source 6 and the motors 3 by product of electric current flowing through the cable 5 to the sensors 4 and resistance of the cable 5 and may lead to a risk that the feedback signals from the sensors 4 are erroneously received by the controller 1.
Furthermore, since the cable 5 is exposed outwardly, noise may penetrate into the cable 5 in an environment having much noise, in which the industrial robot is installed, and there is a risk that accurate detection cannot be performed by the sensors 4. Therefore, in order to obviate this risk, a noise quieting filter has been required to be provided.
Meanwhile, even if the power source 6 for the sensors 4 are provided on the manipulator 2 in the known industrial robot, the power source 6 is caused to branch to the motors 3 of respective axes of the manipulator 2 and thus, the above mentioned problems of potential difference between the power source 6 and the motors 3 and noise cannot be solved. Furthermore, in this case, since the power source 6 is caused to branch to the motors 3 of the manipulator 2, an inconvenience is also incurred since branch portions 7 of the cable become complicated.
In addition, in case the earlier mentioned resetting cables for resetting the backup values of the manipulator 2 are provided for maintenance of the sensors 4, a phenomenon associated with the resetting cables may happen as follows. Since the backup values of the manipulator 2 are erroneously reset due to noise referred to above, the resetting cables should be shortened and thus, each resetting cable is required to be terminated at a connector 8 provided on the manipulator 2 as shown in FIG. 4. Therefore, since each resetting cable is confined to a short interval between the sensor 4 and the connector 8, it is difficult to perform an operation for resetting the backup values of the manipulator 2 at the time of maintenance of the sensors 4.